Hmm, interesting I always found my salifert tests to very between kits, and a few years back ran into a number of issues with them misreading. I ended up switching to ELOS which worked for a while, then I found a discrepancy between 2 kits (I always do a test w/the new kit and the old before I make the switch). So I switched back to Salifert where I found a HUGE difference between Elos & Salifert. My Salifert kit was reading 2dkh higher then my elos. Finally I figured I would try the Hanna, hoping it would at least leave out any guess work done by my eye. I found my hanna to read slightly less then my salifert. Now I'm just kinda at a loss, but I shoot for 8-8.5dkh hoping that if I'm off by +/- 1.5 I'm "ok". As long as I get constant results. I'm a happy camper. It's the best I can ask for I guess? Unfortunately.. I've spent the past month trying to re-dial in my dosers as my alk is doing something weird things. I do hope it's not the tester..